Several additives for food, feed and cosmetics are regarded labile, such as colourants, vitamins, vaccines or enzymes.
Additives can be chemically or enzymatically incompatible with other compounds present in a composition. Otherwise, additives can be heat labile and therefore tend to be deactivated during processing steps which occur at an elevated temperature. For example, feed or food is often prepared by using an extrusion process. These extrusion processes are necessary for obtaining food or feed particles in the required shape. Furthermore, there is a growing tendency to include all sorts of additives to a basic feed or food. Feed or food compositions are more often prepared complete with additives which previously used to be added independently.
Several solutions have been suggested to overcome degradation of a labile compound. One solution is the addition of the desired compounds subsequent to a process step at elevated temperature, e.g. after the extrusion process. Different reports have been published concerning formulations of labile compounds and/or for methods to add such compounds to feed or food particles.
DE 2602260 describes the use of a suspension of an enzyme in a liquid or a molten edible fat. After cooling of the mixture the material has to be particularized. After rough destruction the particles are further treated for example by milling. This process has the disadvantage that the milling of powders to guarantee a small particle size is very tedious and leads to undesirable dusts.
International Patent Application WO 93/14645 solves the problem by addition of an oil suspension containing the heat-labile compounds after the extrusion process. The addition of the suspension to the pellets is performed under lowered pressure.
International Patent Application WO 92/06599 describes the use of a water-in-oil emulsion for protecting vaccines. There is no mentioning of the use of a (protein) stabilizing (i.e. a water activity lowering) agent as part of the emulsion. The formulation of labile compounds such as enzymes in such an emulsion would give rise to a rapid loss of enzymes activity. This loss may amount to 50% per month in hot climates which is unacceptable for commercial products. This patent application also describes the preferred application of a lecithin-based emulsifier.
International Patent Application WO 93/16175 describes a stabilized, aqueous enzyme solution comprising urea and/or a polyol as stabilizing agent. Urea and polyols are known agents to stabilize an enzyme in an aqueous environment.
In the area of cosmetics there also is a growing tendency to include labile compounds in oil containing end products. Especially compounds aimed at skin protection, cleansing and rejuvenation are of obvious interest. Labile compounds claimed to have beneficial effects in this respect include enzymes, such as proteases.
To guarantee enzyme activity in cosmetic formulations over extended shelf life periods, essentially water-free, hydrophobic compounds such as waxes, plant or mineral oils commonly are used as enzyme formulation agents. Although this approach implies a high storage stability of the enzyme in the cosmetic formulation, a serious disadvantage is that the enzyme can only be activated by exposing the formulations to relatively large quantities of water (during which the initially water-free enzyme, is dissolved). An inherent problem is that enzyme activation is relatively slow and that much of the initial enzyme activity is wasted. This approach is not very convenient in several cosmetic applications.
In an alternative approach as described in J03004791, protein decomposing enzymes to be used in cosmetics are stabilized by adding polysaccharides to aqueous solution of the enzymes. Although this approach minimises the use of water needed to re-activate the enzyme, the approach disregards the need for a lipophilic phase in many cosmetic formulations.